The Fowler 52-471-004 telescoping gage is a easy solution when needing to take a fast bore measurement. Telescoping gages have constant spring tension pushing out the measuring contacts. The measuring contacts should be depressed and locked into place toward the minimum end of the range. The telescoping gage should then be inserted into the bore to be measured. Once in the bore, the knurled knob should be turned to release the measuring contacts so both measuring contacts are pressing firmly against the bore walls. The user should them tighten the knurled knob while the measuring contacts are pressed against the bore wall. The gage can then be taken out of the bore with the measuring contacts in the same orientation as when the telescoping gage was in the bore. In order to obtain the final bore measurement, a micrometer should be used to measure over the measuring contacts. A caliper could be used to obtain the final diameter but users will get a more accurate measurement using a micrometer.

The Fowler Telescoping Gages are offered as individual gages as well as sets: